Art. 58 OG; appeal admissibility depends on whether the challenged decision is a main judgment; an enforcement or exequatur decision is not a main judgment. The decisive criterion is the substance of the decision, not its external form. A decision that merely determines enforceability of a foreign judgment, without adjudicating the underlying civil claim, is a procedural enforcement decision and cannot found a federal appeal as a final merits judgment (consid. 1).